JP2012129184A - Radiation tube device and radiation image photography system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent degradation of an X-ray tube of a small focal point and multibeam which is caused by the heat of an anode.SOLUTION: On a beam radiation surface 29 of an anode body 30 of a rotary anode used for an X-ray tube, there are provided a plurality of X-ray non-generating parts 35a-35d consisting of a groove 33, a first X-ray non-generation material 37 provided on the surface of the groove 33, and a second X-ray non-generation material 34 embedded in the groove 33, as well as a plurality of X-ray generating parts 36a-36c which are provided among the X-ray non-generating parts 35a-35d, comprising the surface of the beam radiation surface 29. When an electron beam is emitted from a cathode, the X-ray generating parts 36a-36c generate such X-ray as of wavelength band and intensity suitable for radiation image photographing, to provide a plurality of virtual point light sources arrayed at a predetermined pitch, with a miniaturized focal point. The first X-ray non-generation material 37 and the second X-ray non-generation material 34 are made from, for example, carbon and aluminum, to radiate heat of the anode body 30.

Description

  The present invention relates to a radiation tube device used for capturing a phase contrast image and a radiation image capturing system using the radiation tube device.

  It is known that radiation, for example, X-rays, changes in intensity and phase due to interaction when incident on an object, and the change in phase exhibits an interaction higher than the change in intensity. Using this X-ray property, based on the phase change (angle change) of the X-ray by the subject, a high-contrast image (hereinafter referred to as a phase contrast image) is obtained from the subject having a low X-ray absorption capability. Research on line phase imaging has been actively conducted.

  An X-ray imaging system using a Talbot-Lau interferometer is known as an X-ray phase imaging apparatus (see, for example, Patent Document 1). This X-ray imaging system partially shields X-rays emitted from an X-ray source having a general normal size X-ray focal point (for example, about 0.1 to 1 mm) by a multi-slit, and has a narrow width. A plurality of virtual X-ray sources that are linear and arranged at a predetermined pitch are formed. Since the virtual X-ray source formed by the multi-slits has a small focal spot size, it is possible to obtain the optimal spatial coherence for X-ray phase imaging. Can be increased.

  In the X-ray imaging system, the first grating is arranged so as to face the multi-slit, and the second grating is arranged downstream from the first grating by the Talbot interference distance. Behind the second grating, an X-ray image detector (FPD: Flat Panel Detector) that detects X-rays and generates an image is arranged. Then, a fringe image is generated by the first and second gratings from the X-rays transmitted through the subject arranged between the multi slit and the first grating, and a change in the fringe image is detected by the fringe scanning method. Thus, phase information of the subject is acquired (see, for example, Patent Document 1 and Non-Patent Document 1).

  In the fringe scanning method, the second grating is arranged in parallel to the first grating surface in a direction substantially parallel to the plane of the first grating and substantially perpendicular to the grating direction (strip direction) of the first grating. The image is taken a plurality of times while being translated at a scanning pitch obtained by equally dividing the lattice pitch, and the angle distribution of X-rays refracted by the subject (differentiating the phase shift) from the change in each pixel value obtained by the X-ray image detector. Image), and a phase contrast image of the subject is obtained based on this angular distribution. This fringe scanning method is also used in an imaging apparatus using laser light (see, for example, Non-Patent Document 2).

  The multi-slit needs to have a sufficient thickness in order to guarantee the function of the portion that should absorb X-rays. Moreover, the multi-slit needs to have a slit width of about 10 microns at intervals of several tens of microns. For this reason, the multi-slit has a high aspect ratio structure and is difficult to manufacture. Furthermore, since X-rays spread radially from the generation source, an X-ray multi-slit having a high aspect ratio should ideally be a cylindrical surface with the X-ray source as the center of curvature. This also makes it difficult to produce multi-slits.

  Conventionally, an X-ray source has been invented in which X-rays can be reduced in focus and beam size in the same manner as an X-ray source using a multi-slit without using a multi-slit that is difficult to manufacture. This X-ray source has a narrow and linear line by arranging, in a stripe shape, anodes that generate X-rays by electron beam irradiation on a support substrate formed of a material that does not generate X-rays by electron beam irradiation. A plurality of virtual X-ray sources arranged at a predetermined pitch are formed (see, for example, Patent Document 2).

  Patent Document 3 discloses a multi-beam X by using an anode in which a high-Z material having a large atomic number such as tungsten or molybdenum and a low-Z material having a small atomic number such as aluminum or beryllium are alternately arranged. A radiation source is disclosed. Patent Document 4 discloses an X-ray image capturing system that can capture a phase contrast image by Talbot interferometry using the X-ray source disclosed in Patent Document 3.

Special table 2008-545981 JP 2009-195349 A Chinese publication CN1917135 US Publication US2010 / 0091947

C. David, et al., Applied Physics Letters, Vol. 81, No. 17, October 2002, p. 3287 Hector Canabal, et al., Applied Optics, Vol.37, No.26, September 1998, 6227

  In the X-ray tube, the conversion rate of energy converted to X-rays is 1% or less of the total energy of the electron beam irradiated to the anode, and the remaining 99% or more is heated to heat the anode. It has been known. In Patent Document 3, a low Z material having a low current number is used. However, since such a material has a low melting point alone, it can be melted by heating by irradiation with an electron beam, or a high Z material and a low Z material. There is a concern that the anode may deteriorate due to alloying.

  An object of the present invention is to prevent deterioration of an anode due to heat in a radiation tube apparatus having a small focus and a multi-beam.

  In order to solve the above-mentioned problems, a radiation tube apparatus according to the present invention is provided with a cathode for emitting an electron beam, an anode body having a beam irradiation surface to which an electron beam is irradiated, and an electron beam irradiation provided on the beam irradiation surface. A plurality of radiation generators that generate radiation that can be captured by radiation, and a plurality of radiation generators that are arranged between the radiation generators and that do not generate radiation that can be used for capturing radiation images by irradiation with an electron beam The radiation non-generating part includes a groove provided on the beam irradiation surface and a radiation non-generating material composed of two or more elements and embedded in the groove. Yes.

  It is preferable that at least one element having an atomic number of 30 or less is included in the two or more elements constituting the radiation non-generating material. The non-radiation generating material may be composed of a first non-radiation generating material provided on the surface of the groove and a second non-radiation generating material embedded in the groove. In this case, each of the first and second radiation non-generating materials is preferably composed of a single element or a compound of two or more elements. Another radiation non-generating material may be a compound of two or more elements.

  The anode is provided with a multi-beam generator that emits a plurality of radiation beams by a plurality of radiation generators and non-radiation generators, and a single beam generator that emits a radiation beam by one radiation generator, You may provide the electron beam switching means to selectively irradiate an electron beam to a multi-beam generation part and a single beam generation part.

  In addition, the anode is provided with a plurality of multi-beam generators in which the arrangement intervals of the radiation beams to be emitted are made different by changing the arrangement intervals of the plurality of radiation generating portions and the non-radiation generating portions. There may be provided electron beam switching means for selectively irradiating the multi-beam generator.

  When the anode is a disc-shaped rotating anode, the ray generating portion and the radiation non-generating portion may be provided in an annular shape on the beam irradiation surface provided on the anode plate.

  In the radiographic imaging system of the present invention, a lattice structure composed of a part that transmits radiation and a part that absorbs radiation is periodically arranged, and the first periodic pattern image is formed by passing the radiation irradiated from the radiation source. A first grating, intensity modulating means for applying intensity modulation to the first periodic pattern image at at least one relative position having a phase different from that of the first periodic pattern, and first intensity generated at the relative position by the intensity modulating means. A radiation image detector for detecting two periodic pattern images, and an arithmetic processing means for imaging phase information based on at least one second periodic pattern image detected by the radiation image detector, The radiation tube apparatus of the present invention is used as the radiation stirrer.

  As the intensity modulation means, a second grating in which a grating structure composed of a portion that transmits and absorbs the first periodic pattern is periodically arranged, and one of the first and second gratings, The scanning unit may be configured to move at a predetermined pitch in the periodic direction of the grating structure of the first and second gratings, and each position moved by the scanning unit may correspond to a relative position.

  According to the present invention, since the radiation non-generating part is constituted by the radiation non-generating material composed of two or more kinds of elements, the melting point of the radiation non-generating part is increased and the thermal conductivity is also improved. Degradation of the anode due to heat can be suppressed. Moreover, it can also prevent that a radiation generation part and a radiation non-generation part alloy by comprising a radiation non-generation part with the radiation non-generation material comprised by 2 or more types of elements.

  Since at least one element having an atomic number of 30 or less needs to be included in the two or more types of elements constituting the radiation non-generating material, various materials can be used as the radiation non-generating material. Moreover, since the radiation non-generating material can be the first and second radiation non-generating materials or a compound of two or more kinds of elements, it can be used in various configurations.

  In addition, since it is possible to switch between a single beam and a multi-beam of radiation, it is possible to use optimal radiation for capturing a phase contrast image and capturing an absorption image. Furthermore, since the pitch of the multi-beam can be switched, the image quality of the phase contrast image can be improved. According to the radiographic imaging system of the present invention, since the radiation tube apparatus of the present invention is used, the image quality of the phase contrast image can be improved.

It is a schematic diagram which shows the structure of the X-ray imaging system of this invention. It is the schematic which shows the structure of the X-ray tube of 1st Embodiment of this invention. It is a top view of the rotation anode of a 1st embodiment. It is principal part sectional drawing of the anode plate of 1st Embodiment. It is explanatory drawing which shows the manufacturing procedure of the anode plate of 1st Embodiment. It is a graph which shows the characteristic of the X-ray generated from molybdenum and aluminum. It is explanatory drawing which shows the relationship between the pitch of a point light source, and the grating | lattice pitch of a 1st and 2nd absorption type grating | lattice. It is explanatory drawing which shows the X-ray tube of 2nd Embodiment. It is explanatory drawing which shows the X-ray tube of 3rd Embodiment. It is explanatory drawing which shows the X-ray tube of 4th Embodiment.

[First Embodiment]
As shown in FIG. 1, an X-ray imaging system 10 of the present invention is arranged so as to be opposed to an X-ray source 11 that irradiates a subject H with X-rays, and the X-ray source 11. And an imaging unit 12 for generating image data by detecting the X-rays transmitted through the. A memory 13 for storing image data read from the imaging unit 12 is connected to the imaging unit 12. The memory 13 performs phase processing on a plurality of image data stored in the memory 13 and performs phase contrast image processing. And an image processing unit 14 for recording the generated phase contrast image in the image recording unit 15 is connected. The X-ray source 11 and the imaging unit 12 are controlled by the imaging control unit 16. The system control unit 18 comprehensively controls the entire X-ray imaging system 10 based on operation signals input from the console 17 including an operation unit and a monitor.

  The X-ray source 11 includes a rotary anode type X-ray tube device 20 shown in FIG. 2, a high voltage generator and a collimator (not shown), and the like. The X-ray tube apparatus 20 irradiates the subject H with X-rays based on the control of the imaging control unit 16. The collimator limits the irradiation field so as to shield a portion of the X-rays emitted from the X-ray tube device 20 that does not contribute to the examination region of the subject H.

  The X-ray tube device 20 includes a vacuum envelope 21, a rotating anode 22 and a cathode 23 accommodated in the vacuum envelope 21. The vacuum envelope 21 includes a glass tube 25 whose inside is in a vacuum state, a metallic case body 26 covering the outside of the glass tube 25, and insulating oil sealed between the glass tube 25 and the case body 26. 27. The case body 26 is provided with a radiation port 26a that emits X-rays. The X-ray tube device 20 naturally includes a bearing portion that rotatably supports the rotary anode 22, a rotation mechanism that rotates the rotary anode 22, and the like, but detailed description thereof is omitted in this embodiment.

  The rotating anode 22 includes an anode body 30 having a frustoconical cross section in which a beam irradiation surface 29 inclined toward the other surface is provided on an outer peripheral portion of one surface of a disk, and a center of the anode body 30. And a rotary shaft 31 provided. The cathode 23 is disposed so as to face the beam irradiation surface 29 of the anode body 30 in the axial direction of the rotating shaft 31, and is directed toward the beam irradiation surface 29 when a high voltage is applied from the high voltage generator. Irradiate with an electron beam. The anode body 30 is made of, for example, molybdenum or tungsten, and generates X-rays with an X-ray spectrum depending on the material when irradiated with an electron beam. X-rays generated by the anode body 30 are radiated in the radial direction of the rotary anode 22, pass through the radiation port 26 a, and radiate out of the X-ray tube device 20.

  As shown in FIGS. 3 and 4, the beam irradiation surface 29 of the anode body 30 has an annular groove 33, a first X-ray non-generating material 37 provided on the surface of the groove 33, and the inside of the groove 33. Four X-ray non-generating portions 35a to 35d made of the second X-ray non-generating material 34 embedded in the are provided. Between the X-ray non-generating portions 35a to 35d, three annular X-ray generating portions 36a to 36c each including a part of the beam irradiation surface 29 are provided. The X-ray generators 36a to 36c are set to have a width and an interval so that a plurality of minute X-ray focal points suitable for capturing a phase contrast image can be obtained.

  The X-ray non-generating portions 35a to 35d used in the present embodiment do not mean that X-rays are not generated at all, but compared to X-rays having a desired wavelength generated by the X-ray generating portions 36a to 36c. It means a site where X-rays having a wavelength that deviates from a desired wavelength or a sufficiently negligible amount of energy is generated. Regarding the X-rays generated from the X-ray non-generating portions 35a to 35d, the amount of energy that can be sufficiently ignored is, for example, preferably about 1/10 of the X-rays generated from the X-ray generating portions 36a to 36c, more preferably 1 / 100 or so.

  In addition, the first X-ray non-generating material 37 and the second X-ray non-generating material 34 have a characteristic X-ray wavelength of the characteristic X-ray generated by the electron beam irradiation of the material used for the anode body 30. For example, a single element having an atomic number of 30 or less, or a compound of two or more kinds of elements including at least one element having an atomic number of 30 or less can be used.

  As a material of the first X-ray non-generating material 37 having such characteristics, for example, C, SiC, TiC, TaC, BN, GaN, AlN, TiN, TiCN, TiAlN, AlCrN, or the like can be used. Alternatively, the protective layer may be formed by performing ion implantation on the surface of the groove 33 and then performing heat treatment.

As the applicable material to the second X-ray non-generating material 34, for example, other aluminum, Si, Ti, V, Cr , Mn, Fe, Co, Ni, Cu, SiO 2, Al 2 O 3 , BeO ₂ , MgO, TiO ₂ , Si ₃ N ₄ , SiC, BN, AlN, SUS, TiC, WC, WCTiCo, GaN, and the like.

  For example, when carbon and aluminum are used as the first X-ray non-generating material 37 and the second X-ray non-generating material 34, since carbon and aluminum have high thermal conductivity, the second X-ray non-generating material 34 is used. Can be prevented from melting. Further, since the carbon constituting the first X-ray non-generating material 37 has a high melting point and is thermally stable, the reaction between the anode body 30 and the second X-ray non-generating material 34 is suppressed. Alloying can be prevented. Thereby, the intensity | strength of the anode main body 30 with respect to a heat | fever improves.

  The rotary anode 22 is manufactured as follows, for example. As shown in FIG. 5A, a disk-shaped metal plate 38 made of a metal such as tungsten or molybdenum is prepared. Next, as shown in FIG. 4B, the outer peripheral portion is cut from one surface of the metal plate 38 to form a beam irradiation surface 29, and the cross-sectional shape of the metal plate 38 is shaped into a truncated cone-shaped anode body 30. To do. As shown in FIG. 3C, four annular grooves 33 are formed on the beam irradiation surface 29 of the anode body 30 by groove cutting or etching.

  As shown in FIG. 5D, the first X-ray non-generating material 37 is formed on the surfaces of the plurality of grooves 33 formed in the anode body 30. The first non-X-ray generating material 37 can be formed by sputtering, ion plating, CVD, or the like, for example. The thickness of the first non-X-ray generating material 37 is preferably about 10 nm to 10 μm, for example, although it varies depending on the material and the like.

  As shown in FIG. 5E, a second X-ray non-generating material 34 made of aluminum or the like is formed on the upper surface of the anode body 30 by plating or vapor deposition. The second X-ray non-generating material 34 formed on the anode body 30 is also filled in the four grooves 33. Next, as shown in FIG. 5F, the second X-ray non-generating material 34 on the surface of the anode body 30 is removed by a polishing apparatus. The second non-X-ray generating material 34 filled in the groove 33 remains without being removed by polishing. Thereby, it is provided between the X-ray non-generating parts 35a to 35d made of the groove 33, the first X-ray non-generating material 37 and the second X-ray non-generating material 34 and the X-ray non-generating parts 35a to 35d. Thus, the rotary anode 22 including the X-ray generators 36a to 36c is completed.

  The electron beam emitted from the cathode 23 is applied to the beam irradiation surface 29 of the anode body 30 that rotates about the rotation axis 31. Then, X-rays are generated from the X-ray generators 36a to 36c and the non-X-ray generators 35a to 35d on the beam irradiation surface 29 with X-ray spectra depending on the respective materials.

  The X-ray spectrum includes a characteristic X-ray having a specific energy and a continuous X-ray component that is weaker but includes various energy components. As shown in FIG. 6, a wavelength region including characteristic X-rays generated from molybdenum is used in, for example, an X-ray imaging apparatus. On the other hand, characteristic X-rays generated from aluminum are not included in the above wavelength range because of their low energy, and most of them are not observed because they are absorbed by air. Also, continuous X-rays from aluminum are quite weak because the total intensity of continuous X-rays is almost proportional to the square of the atomic number of the material. Therefore, the generated X-ray intensity varies greatly depending on the material. Further, since the electron beams irradiated to the X-ray non-generating portions 35a to 35d are all absorbed by the first X-ray non-generating material 37 and the second X-ray non-generating material 34 and do not reach the anode body 30. X-rays are not generated from the anode body 30 at positions facing the lower surfaces of the X-ray non-generating portions 35a to 35d.

  As described above, in the present embodiment, X-rays in a wavelength region suitable for capturing an X-ray image are generated by the X-ray generators 36a to 36c and emitted from the radiation port 26a to the outside of the X-ray tube device 20. Further, as shown in FIG. 7, these X-rays have a minute focal spot size and are arranged at a predetermined pitch, so that a plurality of minute point light sources 11a having a minute size suitable for capturing a phase contrast image. ˜11c can be formed.

  As shown in FIG. 1, the imaging unit 12 includes a flat panel detector (FPD) 40 formed of a semiconductor circuit, and a first for performing phase imaging by detecting a phase change (angle change) of X-rays by the subject H. An absorption type grating 41 and a second absorption type grating 42 are provided. The FPD 40 is arranged so that the detection surface is orthogonal to a direction along the optical axis A of X-rays irradiated from the X-ray source 11 (hereinafter referred to as z direction).

In the first absorption type grating 41, a plurality of X-ray shielding portions 41a extending in one direction in the plane orthogonal to the z direction (hereinafter referred to as the y direction) has a direction orthogonal to the z direction and the y direction (hereinafter referred to as the y direction). the x that direction) in which are arranged at a predetermined pitch p _1. Similarly, the second absorption grating 42 has a plurality of X-ray shielding portions 42a which extend in the y direction, in which are arranged at a predetermined pitch p ₂ in the x-direction. As a material of the X-ray shielding portions 41a and 42a, a metal excellent in X-ray absorption is preferable. For example, gold, platinum, silver, tungsten, molybdenum, tantalum, niobium, palladium, rhodium, iridium, osmium, rhenium, and their Alloys are preferred.

  In addition, the imaging unit 12 moves the second absorption type grating 42 relative to the first absorption type grating 41 by translating the second absorption type grating 42 in a direction orthogonal to the grating direction (x direction). A scanning mechanism 43 that changes the relative position is provided. The scanning mechanism 43 is configured by an actuator such as a piezoelectric element, for example. The scanning mechanism 43 is driven based on the control of the imaging control unit 16 at the time of stripe scanning described later. As will be described in detail later, the memory 13 stores image data obtained by the photographing unit 12 at each scanning step of fringe scanning. The second absorption type grating 42 and the scanning mechanism 43 constitute intensity modulation means described in the claims.

  The image processing unit 14 generates a phase differential image based on a plurality of image data captured by the imaging unit 12 at each scanning step of fringe scanning and stored in the memory 13, and integrates the phase differential image along the x direction. By doing so, a phase contrast image is generated. The phase contrast image is recorded in the image recording unit 15 and then output to the console 17 and displayed on a monitor (not shown).

  In addition to the monitor, the console 17 includes an input device (not shown) through which an operator inputs a shooting instruction and the content of the instruction. As this input device, for example, a switch, a touch panel, a mouse, a keyboard or the like is used, and an X-ray imaging condition such as a tube voltage of the X-ray tube or an X-ray irradiation time, an imaging timing, etc. are input by operation of the input device. The The monitor is composed of a liquid crystal display or a CRT display, and displays characters such as X-ray imaging conditions and the phase contrast image.

As shown in FIG. 7, X-ray shielding portion 41a of the first absorption grating 41 at a predetermined pitch p ₁ in the x direction, and are arranged at a predetermined interval d ₁ from each other. Similarly, X-rays shielding portions 42a of the second absorption grating 42 at a predetermined pitch p ₂ in the x direction, and are arranged at a predetermined interval d ₂ from each other. The light source 11a~11c that it is virtually formed by the X-ray tube device 20 are arranged at a predetermined pitch _{p 3} in the x-direction. The X-ray shielding portions 41a and 42a are each disposed on an X-ray transmissive substrate (for example, a glass substrate) (not shown). The first and second absorption gratings 41 and 42 do not give a phase difference to incident X-rays but give an intensity difference, and are also referred to as amplitude gratings. Incidentally, (a region of the interval d _1, d ₂₎ slit portion may not be a void, X-rays low absorption material such as a polymer or light metal may be filled.

The first and second absorption gratings 41 and 42 are configured to linearly project the X-rays that have passed through the slit portion regardless of the presence or absence of the Talbot interference effect. Specifically, by setting the distances d ₁ and d ₂ to a value sufficiently larger than the peak wavelength of X-rays emitted from the X-ray source 11, most of the X-rays included in the irradiated X-rays are slit at the slit portion. It is configured to pass through without being diffracted while maintaining straightness. For example, when tungsten is used as the rotating anode of the aforementioned X-ray tube and the tube voltage is 50 kV, the peak wavelength of the X-ray is about 0.4 mm. In this case, if the distances d ₁ and d ₂ are about ₁ to 10 μm, most of the X-rays are projected linearly without being diffracted by the slit portion. In this case, the lattice pitches p ₁ and p ₂ are about ₂ to 20 μm.

Since the X-ray irradiated from the X-ray source 11 is not a parallel beam but a cone beam having an X-ray focal point as a light emitting point, the first periodic pattern projected through the first absorption grating 41 A projected image that is an image (hereinafter, this projected image is referred to as a G1 image or a fringe image) is enlarged in proportion to the distance from the virtual point light sources 11a to 11c. The grating pitch p ₂ and the interval d ₂ of the second absorption type grating 42 are determined so that the slit portions thereof substantially coincide with the periodic pattern of the bright part of the G1 image at the position of the second absorption type grating 42. Yes. That is, the distance from the point light source 11a~11c to the first absorption type grating 41 _{L 1,} the distance from the first absorption grating 41 to the second absorption grating 42 in case of the _{L 2,} the grating pitch p ₂ and the interval d ₂ are determined so as to satisfy the relationship of the following expressions (1) and (2).

In the case of a Talbot interferometer, the distance L ₂ from the first absorption type grating 41 to the second absorption type grating 42 is limited to the Talbot interference distance determined by the grating pitch of the first grating and the X-ray wavelength. However, in the imaging unit 12 of the present embodiment, the first absorption type grating 41 projects the incident X-rays without diffracting, and the G1 image of the first absorption type grating 41 is the first image. because similarly obtained at all positions of the back absorption grating 41, the distance L _2, can be set independently of the Talbot distance.

The pitch _{p 3} of the point light source 11a~11c is set so as to satisfy the following equation (3).

  In the above formula (3), the projection image (G1 image) of the X-rays emitted from the respective point light sources 11a to 11c formed by the X-ray tube device 20 by the first absorption type grating 41 is the second absorption type. This is a geometric condition for matching (overlapping) at the position of the lattice 42. As described above, in the present embodiment, the G1 images based on the plurality of point light sources 11a to 11c formed by the X-ray tube device 20 are superimposed, so that the image quality of the phase contrast image is reduced without reducing the X-ray intensity. Can be improved.

  Next, the operation of the above embodiment will be described. As shown in FIG. 1, in the X-ray imaging system 10, a subject H is disposed between an X-ray source 11 and an imaging unit 12. In this state, when an imaging instruction is input from the console 17 to the system control unit 18, the imaging control unit 16 controls each part of the X-ray image imaging system 10, and the second absorption type grating 42 is first absorbed. While moving in the x direction with respect to the mold grating 41, exposure by the X-ray source 11 and detection operation by the FPD 40 are performed at each scanning position.

  As shown in FIGS. 2 to 4, the X-ray tube apparatus 20 irradiates the electron beam from the cathode 23 toward the beam irradiation surface 29 of the anode body 30 during the exposure period at each scanning position. The X-ray non-generating portions 35a to 35d and the X-ray generating portions 36a to 36c of the anode body 30 generate X-rays with an X-ray spectrum depending on their materials by irradiation with an electron beam. However, since the X-rays generated from the X-ray non-generating units 35a to 35d do not have an intensity that can be used for X-ray imaging, they are generated from the X-ray tube device 20 by the X-ray generating units 36a to 36c. X-rays are emitted.

  As shown in FIG. 7, X-rays radiated from the X-ray tube device 20 form a plurality of virtual point light sources 11 a to 11 c having a minute focal spot size and arranged at a predetermined pitch p <b> 3. The X-rays of the point light sources 11a to 11c cause a phase difference when passing through the subject H, and the X-rays pass through the first absorption grating 41, so that the refractive index of the subject H and the transmitted optical path length are obtained. A striped G1 image reflecting the transmission phase information of the subject H determined from the above is formed. Since the G1 images of the respective point light sources 11a to 11c are projected onto the second absorption type grating 42 and coincide with each other (overlap) at the position of the second absorption type grating 42, the phase contrast can be achieved without reducing the X-ray intensity. The image quality can be improved.

  The G1 image is intensity-modulated by the second absorption type grating 42 to form a G2 image that is a second periodic pattern image. The G2 image is detected by, for example, a fringe scanning method. In the fringe scanning method, the grating pitch is equally divided in the direction along the grating plane with the X-ray focal point as the center by the scanning mechanism 43 with respect to the first absorbing grating 41 (for example, The X-ray source 11 irradiates the subject H with X-rays while performing translational movement in the x-direction with a scanning pitch divided into five), and performs imaging a plurality of times and detects it by the FPD 40. A method for obtaining a phase differential image (corresponding to an angular distribution of X-rays refracted by the subject) from a phase deviation amount of pixel data of each pixel (phase deviation amount with and without the subject H) It is. The phase differential image of the subject H can be obtained by integrating the phase differential image along the fringe scanning direction by the image processing unit 14. The phase contrast image is recorded in the image recording unit 15 by the image processing unit 14 and displayed on the monitor of the console 17 or the like.

  As described above, the X-ray tube apparatus 20 according to the present embodiment forms the point light sources 11a to 11c without using the multi-slit, and thus can eliminate the multi-slit that is difficult to manufacture. Thereby, it can contribute to size reduction and cost reduction of an apparatus. Furthermore, in this embodiment, since carbon and aluminum having good thermal conductivity are used for the first X-ray non-generating material 37 and the second X-ray non-generating material 34, an anode generated by electron beam irradiation is used. The heat of the main body 30 can be radiated from the X-ray non-generating portions 35a to 35d. The first X-ray non-generating material 37 provided on the surface of the groove 33 suppresses the reaction between the anode main body 30 and the second X-ray non-generating material 34 and prevents alloying. Therefore, it is possible to prevent the anode body 30 from being deteriorated by heat.

  In the above embodiment, the groove 33 of the anode body 30 is arranged in parallel with the rotation shaft 31, but may be arranged in non-parallel with the rotation shaft 31. Further, although the second non-X-ray generating material 34 is embedded to the upper end of the groove 33, the second X-ray non-generating material 34 may be embedded to the middle of the groove 33 in the depth direction. Moreover, in the said embodiment, although carbon was used for the 1st X-ray non-generation material 37 and aluminum was used for the 2nd X-ray non-generation material 34, each other single element mentioned above, or two or more types of elements The same effect as the above embodiment can be obtained.

  Hereinafter, another embodiment obtained by modifying the first embodiment will be described. In addition, about the same structure as other embodiment, detailed description is abbreviate | omitted using a same sign.

[Second Embodiment]
As shown in FIG. 8, the cathode 23 is moved in the horizontal direction by a moving mechanism 55 formed of an actuator such as a piezoelectric element, and a multi-beam generating unit including X-ray non-generating units 35a to 35d and X-ray generating units 36a to 36c. Alternatively, the electron beam may be selectively irradiated between the beam 56 and the single beam generation unit 57 having only the X-ray generation unit, that is, the beam irradiation surface 29 of the anode body 30. According to this, when capturing a phase contrast image, a plurality of virtual point light sources 11a to 11c can be obtained by irradiating the multi-beam generator 56 with an electron beam. Further, when an absorption image is taken, X-rays having a large dose can be obtained by irradiating the single beam generator 57 with an electron beam.

[Third Embodiment]
As shown in FIG. 9, the first multi-beam generation unit 60 including the X-ray non-generation units 35a to 35d and the X-ray generation units 36a to 36c, and the first multi-beam generation unit 60 include the X-ray non-generation units 61a to 61a. A second multi-beam generating unit 63 having a different arrangement interval between 61d and the X-ray generating units 62a to 62c is provided in the anode main body 30, and the first multi-beam generating unit 60 and the second multi-beam generating unit 60 are connected to each other by the cathode 23 moved by the moving mechanism 55. The multi-beam generator 63 may be selectively irradiated with an electron beam. The X-ray non-generating parts 61 a to 61 d are made of a groove and an X-ray non-generating material, like the X-ray non-generating parts 35 a to 35 d, and the X-ray generating parts 62 a to 62 c are made of the beam irradiation surface 29 of the anode body 30.

  According to this, the pitch p3 of the virtual point light sources 11a to 11c formed by the first multi-beam generating unit 60 can be switched, for example, as the pitch p4. For example, the distance L1 between the X-ray source 11 and the first absorption type grating 41, or the distance L2 between the first absorption type grating 41 and the second absorption type grating 42, the lattice pitch of the second absorption type grating 42 If the pitch p3 of the point light sources 11a to 11c is switched in accordance with p2 or the like, a higher-quality phase contrast image can be taken.

  A cathode capable of simultaneously irradiating an electron beam to both the first and second multi-beam generators 60 and 63 is disposed, and X from either one of the first and second multi-beam generators 60 and 63 is disposed. The energy of X-rays to be irradiated may be switched by enabling switching between irradiation of X-rays and irradiation of X-rays from both the first and second multi-beam generators 60 and 63. According to this, energy subtraction imaging using X-rays having different energy bands can be performed.

  In the second and third embodiments, the irradiation position of the electron beam is switched by moving the cathode 23 by the moving mechanism 55. However, the shielding state of the electron beam between the cathode 23 and the anode body 30 is changed. Alternatively, the irradiation position may be switched by deflecting the electron beam by applying a high voltage.

[Fourth Embodiment]
Further, in each of the embodiments described above, the first X-ray non-generating material 37 is provided on the surface of the groove 33 constituting the X-ray non-generating portion. When using a compound composed of two or more elements including at least one element of 30 or less and having a melting point as high as that of carbon, as shown in FIG. X-ray non-generating portions 35a to 35d may be used.

  In each of the above embodiments, an X-ray imaging apparatus using a striped one-dimensional lattice having an X-ray shielding portion that is stretched in one direction and arranged in a direction orthogonal to the stretching direction has been described as an example. The present invention can also be applied to an X-ray imaging apparatus using a two-dimensional lattice in which X-ray shields are arranged in two directions. Furthermore, in the above embodiment, the subject H is disposed between the X-ray source and the first absorption type grating, but the subject H is provided between the first absorption type grating and the second absorption type grating. Similarly, a phase-contrast image can be generated when arranged in between. The above embodiments can be combined with each other within a consistent range.

  In each of the above embodiments, the first and second absorption gratings are configured to linearly project X-rays that have passed through the slit, but the present invention is not limited to this configuration, A configuration in which a so-called Talbot interference effect is generated by diffracting X-rays with the first and second absorption gratings (configuration described in International Publication WO 2004/058070) may be employed. In this case, it is necessary to set the distance between the first and second absorption gratings to the Talbot interference distance. Further, the type of the first absorption type grating may be a phase type grating having a relatively low aspect ratio instead of the absorption type grating.

  In each of the above embodiments, a fringe image whose intensity is modulated by the second absorption type grating is detected by the fringe scanning method to generate a phase contrast image. However, a phase contrast image is generated by one shooting. X-ray imaging systems are also known. For example, in the X-ray imaging system described in International Publication WO2010 / 050484, the moire generated by the first and second gratings is detected by an X-ray image detector, and the intensity of the detected moire is detected. A spatial frequency spectrum is acquired by performing Fourier transform on the distribution, and a differential phase image is obtained by separating the spectrum corresponding to the carrier frequency from this spatial frequency spectrum and performing inverse Fourier transform. The X-ray tube of the present invention can also be used for such an X-ray imaging system.

  In addition, in an X-ray imaging system that generates a phase contrast image by one imaging, a conversion layer that converts X-rays into electric charges and a conversion layer are used as intensity modulation means instead of the second grating. Some use a direct conversion type X-ray image detector having a charge collecting electrode for collecting the collected charges. This X-ray imaging system, for example, electrically connects linear electrodes in which the charge collection electrodes of each pixel are arranged with a period substantially matching the period pattern of the fringe image formed by the first grating. The linear electrode groups are arranged so that their phases are different from each other, and each stripe electrode group is individually controlled to collect charges, thereby acquiring a plurality of fringe images by one photographing. A phase contrast image is generated on the basis of the plurality of fringe images (configuration described in JP 2009-133823 A). The X-ray tube of the present invention can also be used for such an X-ray imaging system.

  Further, as another X-ray imaging system for generating a phase contrast image by one imaging, the first and second gratings are arranged so that the extension direction of the grating is relatively inclined by a predetermined angle. A plurality of fringe images having different relative positions of the first and second gratings are obtained by dividing and capturing a section of a moire cycle that occurs in the stretching direction due to inclination, and a phase contrast image is obtained from the plurality of fringe images. It is also possible to generate. The X-ray tube of the present invention can also be used for such an X-ray imaging system.

  Further, an X-ray imaging system in which the second grating is omitted by using an optical reading type X-ray image detector can be considered. In this system, a first electrode layer that transmits a periodic pattern image formed by a first grating, a photoconductive layer that generates charges upon receiving irradiation of the periodic pattern image transmitted through the first electrode layer, A charge accumulation layer for accumulating charges generated in the photoconductive layer and a second electrode layer in which a large number of linear electrodes that transmit the reading light are arranged in this order, and each linear shape is scanned by the reading light. An optical reading X-ray image detector from which an image signal for each pixel corresponding to the electrode is read is used as the intensity modulation means, and the charge storage layer is formed in a grid pattern with a pitch finer than the arrangement pitch of the linear electrodes. Thus, the charge storage layer can function as the second lattice. The X-ray tube of the present invention can also be used for such an X-ray imaging system.

  The embodiment described above can be applied not only to a radiographic imaging system for medical diagnosis but also to other radiographic systems such as industrial use and nondestructive inspection. Furthermore, in the present invention, gamma rays or the like can be used in addition to X-rays as radiation.

DESCRIPTION OF SYMBOLS 10 X-ray imaging system 11 X-ray source 11a-11c Point light source 12 Image pick-up part 20 X-ray dredge apparatus 22 Rotating anode 23 Cathode 29 Inclined surface 30 Anode plate 33 Groove 34 2nd X-ray non-generation material 35a-35d X-ray Non-generating part 36a to 36c X-ray generating part 37 First X-ray non-generating material 40 Flat panel detector 41 First absorption type grating 42 Second absorption type grating 55 Moving mechanism 56 Multi-beam generation part 57 Single beam generation Unit 60 First multi-beam generating unit 63 Second multi-beam generating unit

Claims (9)

A cathode emitting an electron beam;
An anode main body having a beam irradiation surface irradiated with an electron beam from the cathode, a plurality of radiation generators provided on the beam irradiation surface and generating radiation capable of capturing a radiographic image by irradiation of the electron beam; and An anode having a plurality of radiation non-generating parts that are arranged between the radiation generating parts and that do not generate radiation that can be used for radiographic imaging by irradiation with an electron beam,
The radiation non-generating portion includes a groove provided on the beam irradiation surface and a radiation non-generating material composed of two or more elements and embedded in the groove.   2. The radiation acupuncture apparatus according to claim 1, wherein at least one element having an atomic number of 30 or less is included in the two or more kinds of elements constituting the radiation non-generating material.   The non-radiation generating material includes a first non-radiation generating material provided on a surface of the groove, and a second non-radiation generating material embedded in the groove, and the first and second radiations. The non-generating material is made of a single element or a compound of two or more kinds of elements, respectively.   3. The radiation acupuncture apparatus according to claim 1, wherein the radiation non-generating material is a compound of two or more kinds of elements. The anode includes a plurality of radiation generation units and a radiation non-generation unit, a multi-beam generation unit that emits a plurality of radiation beams, and a single radiation generation unit that emits a single radiation beam. A beam generator,
The radiation tube apparatus according to claim 1, further comprising an electron beam switching unit that selectively irradiates the electron beam to the multi-beam generation unit and the single beam generation unit. The anode has a plurality of multi-beam generation units each having a different arrangement interval of the emitted radiation beam by different arrangement intervals of the plurality of radiation generation units and the radiation non-generation unit,
The radiation tube apparatus according to claim 1, further comprising an electron beam switching unit that selectively irradiates the plurality of multi-beam generation units with the electron beam.   The anode main body is a disk-shaped rotating anode, and the radiation generating part and the radiation non-generating part are arranged in an annular shape on the beam irradiation surface provided on the anode plate. The radiation tube apparatus according to claim 1. A first grating for periodically forming a grating structure composed of a part that transmits radiation and a part that absorbs radiation, and that passes through the radiation irradiated from the radiation acupuncture device to form a first periodic pattern image; Intensity modulating means for applying intensity modulation to the first periodic pattern image at at least one relative position having a phase different from that of one periodic pattern image, and a second period generated at the relative position by the intensity modulating means. A radiation image detector for detecting a pattern image; and an arithmetic processing means for imaging phase information based on at least one second periodic pattern image detected by the radiation image detector;
A radiographic imaging system, wherein the radiation tube apparatus according to claim 1 is used as the radiation acupuncture apparatus.   The intensity modulation means includes: a second grating in which a grating structure composed of a portion that transmits the first periodic pattern and a portion that absorbs the first periodic pattern is periodically arranged; and one of the first and second gratings And a scanning means for moving at a predetermined pitch in the periodic direction of the lattice structure of the first and second gratings, and each position moved by the scanning means corresponds to the relative position. The radiographic imaging system according to claim 8.

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